Rich running CB750F

[Ed750F]

Bike is a 1977 CB750F Super Sport. 24,500 original miles.  It sat for 12+ yrs. Had the F2 carbs ("key hole" type) redone (needed to). Left them stock. Runs strong, Idles OK.
 1- Sometimes it will not return to 1200rpms when stopping in traffic, hangs up around  2200rpms, if I let clutch out to to drop rpm it will go to 1200 and hold it.
 2- My main problem. Running very rich, exhaust is BLACK and getting around 30mpg.
Had float levels check and rechecked. Carbs were synchronized, new carb mounts, new stock air filter and housing.
Valve adjustment also set and reset, Timing also double checked. Put a Pamco electronic ignition with new coils, wires, plug caps and plugs
Can not find anybody in my area that knows this bike or will touch the carbs.
Any help will be greatly appreciated.
Thank you, Eddie

[TOOLS1]

Several things could be going on here. You have a vacuum leak, you are running lean, your carbs are terribly out of sync. All of these can cause the hanging idle. However I am going to say that whoever worked on your carbs did not install the little O-rings and washers on the fuel/pilot screws. That will make it run rich with a lean hanging idle.
Where are you located that there is not anyone that wants to work on your bike?
TOOLS

[Ed750F]

I am in Newburgh NY. the 3 Honda dealers in my area don't want to work on OLD bikes or don"t have anybody that know them. The guy who did the carbs was a Honda dealer owner and Honda trained on the 750s.
I looked up "oldmanhonda". his tune up info as the CB750F float levels as 26mm/1.02in. my floats are set to 14.5mm/0.57in. If this is wrong will it cause my problems??

[TOOLS1]

Yea, the dealers will not work on anything over a few years old. You will need to find an independent repair shop if you want someone to work on your bike. Some of these shops are really good, and some are just ripoff hacks. Do your research before taking your bike to them.
As for the float height, the float is only an on/off switch to control the fuel level in the carb. As long as the fuel is not running out of the carbs, or the bike is not acting lie it is running out of fuel at high RPMs it is good. Even though your carbs were worked on by a Honda trained mechanic does not mean they are good. How long has it been since he rebuilt them? What parts did he replace? Where did he source these parts? I have had a lot of problems with aftermarket carb parts. A little variation in the machining can cause big problems. I am pretty sure that there is a problem with the fuel/pilot screws on your carbs.
TOOLS

[Ed750F]

Carbs were done about a year ago but carbs were not put on bike until 2 weeks ago. Rebuild kits came from VintageCB750.com (#48-1737) out of Canada. Kits made in Japan.
I will take out the  pilot screws and check them. When reinstalling them "oldmanhonda" has setting at 1 turn out vs. 1 3/4 turn as in book for preliminary setting. Will try his way first. Will let you know what I find with pilot screws.
I hope this solves the problems, as they are the last of a long list.
Thank you for your help and insight. Ed

[TOOLS1]

HondaTOOLS would start with the factory setting since that would be a "richer" setting, and your hanging idle is a symptom of a lean setting. Also the ethanol we have now tends to make an engine run leaner. I have had to set them out as much as 3 1/4 turns.
HondaTOOLS

[Ed750F]

Removed carbs and pilot screws. Found #1 pilot screw had washer under spring so spring was in direct contact with o-ring. 2,3,4 were installed - spring, washer,o-ring on pilot screw as removed. Checked passages to make sure they were clear, they were. Reassembled and set pilot screws to 1 turn out. Installed carbs. Started. Fired right up an idled at 1200 rpms. Cracked throttle several times and rpms returned to 1200 idle. Still getting a black cloud when I snap open throttle. At least I know the accelerator pump is working.
Road test will be another day.